2 min soln needed for the Work rate EP2
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 Neilsheth2
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First sentence tells you that X's rate is (1/4 tank)/2 hrs = 1/8 tank/hr
The third sentence tells you that Y's rate is (3/4 tank)/18 hrs = 1/24 tank/hr
Both of which allow you to set up the following:
3/4 tank remaining = 3 hrs( 1/8 + 1/24 +Z)
Therefore, 3/12 tank/hr = 6/24 tank/hr = 3/24 + 1/24 + Z > Z = 2/24 or 1/12 tank/hr = 12 hrs/tank
The third sentence tells you that Y's rate is (3/4 tank)/18 hrs = 1/24 tank/hr
Both of which allow you to set up the following:
3/4 tank remaining = 3 hrs( 1/8 + 1/24 +Z)
Therefore, 3/12 tank/hr = 6/24 tank/hr = 3/24 + 1/24 + Z > Z = 2/24 or 1/12 tank/hr = 12 hrs/tank
 OptimusPrep
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Assume total volume of the tank = 8 units.Neilsheth2 wrote:Hi how can we easily solve this question?
Rate of X = 1 units/hour.
Remaining amount of water = 6 units.
Rate of pump Y = 6/18 = 1/3 units/hour
Time taken by all 3 to remove 6 units of water = 3 hours.
(1 + Y + 1/3 )*3 = 6
3Y + 4 = 6
Y = 2/3 units/hour
Time taken by Y to employee full tank = 8 / (2/3) = 12 hours.
Correct Option: B